* {
  box-sizing: border-box;
}

ul {
  margin: 0;
  padding: 0;
}

h2 {
  font-family: '楷体';
}

ul li {
  cursor: pointer;
  position: relative;
  padding: 12px 8px 12px 40px;
  background: #eee;
  font-size: 28px;
  font-family: '华文新魏';
  transition: 0.2s;
  user-select: none;
}

ul li:nth-child(odd) {
  background-color: #ddd;
}

ul li.checked {
  background-color: dodgerblue;
  color: #ffffff;
}

ul li.checked::before {
  content: '';
  position: absolute;
  border-color: #fff;
  border-style: solid;
  border-width: 0 2px 2px 0;
  top: 10px;
  left: 16px;
  transform: rotate(45deg);
  height: 15px;
  width: 7px;
}

.close {
  position: absolute;
  right: 0;
  top: 0;
  padding: 12px 16px 12px 16px;
}

.close:hover {
  background-color: #f44336;
  color: white;
}

.header {
  background-color: #f44336;
  padding: 30px 40px;
  color: white;
  text-align: center;
}

/* 清除浮动 */
.header:after {
  content: '';
  display: table;
  clear: both;
}

/* 输入框样式 */
input {
  border: none;
  width: 75%;
  padding: 10px;
  float: left;
  font-size: 16px;
  outline: 0;
}

/* “添加”按钮样式 */
.addBtn {
  padding: 10px 10px 8px;
  width: 25%;
  background: #d9d9d9;
  color: #555;
  float: left;
  text-align: center;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: 0.3s;
}

.addBtn:hover {
  background-color: #bbb;
}
